Operating Frequency Bandwidth Research Articles

Wideband <inline-formula> <tex-math notation="LaTeX">$W$ </tex-math> </inline-formula>-Band Substrate-Integrated Waveguide Magnetoelectric (ME) Dipole Array Antenna

In this communication, a W-band substrate-integrated waveguide (SIW) magnetoelectric (ME) dipole array antenna is reported with a wide operating bandwidth. By combing a longitudinal slot, which is functioned as a magneto dipole, on the top surface of the SIW, and a loaded short-circuited patch functioned as an electric dipole, an SIW ME dipole is designed. Thus, both merits of the low-loss character of the SIW and the wideband performance of the ME dipole are utilized. The proposed technique is capable of designing a large planar array with a wide operating bandwidth. As a demonstration, a W-band $4\times 8$ SIW array antenna is designed and fabricated by using a low-cost printed circuit board technology. The experimental results show that the 10 dB impedance bandwidth of the designed prototype is 13.89%, i.e., from 78.4 to 90.1 GHz. Stable radiation patterns, high radiation efficiencies, and low cross-polarization levels are achieved within a wide operating frequency band. In addition, a stable gain of 19.6±0.7 dBi is obtained as well. The proposed antenna is a good candidate for the millimeter-wave wireless system.

Miniaturized frequency-agile bandpass filter integrated single-pole double-throw switch

This article presents a miniaturized frequency-agile bandpass filter (BPF) integrated single pole double throw (SPDT) switch using common LC resonator. The BPF-integrated on-sate channel is constituted by the capacitively coupled LC resonators with loaded varactor diodes and reverse-biased p-i-n diodes. The off-state channel with high suppression is built when the p-i-n diodes loaded LC resonators is forward-biased. As an example, a frequency-agile BPF-integrated SPDT switch with constant 3-dB fractional bandwidth of 18.4% is designed. Its fabricated circuit area including bias circuit but excluding feeding lines is 0.105 λg × 0.079 λg. Measured results show that its 3 dB operating frequency bandwidth covers from 0.499 to 1.077 GHz with in-band insertion loss varying from 4.15 to 3.15 dB. Off-state suppression better than 37.8 dB, port-to-port isolation better than 51.1 dB, and good return loss can be also observed.

Manipulating acoustic wave reflection by a nonlinear elastic metasurface

The acoustic wave reflection properties of a nonlinear elastic metasurface, derived from resonant nonlinear elastic elements, are theoretically and numerically studied. The metasurface is composed of a two degree-of-freedom mass-spring system with quadratic elastic nonlinearity. The possibility of converting, during the reflection process, most of the fundamental incoming wave energy into the second harmonic wave is shown, both theoretically and numerically, by means of a proper design of the nonlinear metasurface. The theoretical results from the harmonic balance method for a monochromatic source are compared with time domain simulations for a wave packet source. This protocol allows analyzing the dynamics of the nonlinear reflection process in the metasurface as well as exploring the limits of the operating frequency bandwidth. The reported methodology can be applied to a wide variety of nonlinear metasurfaces, thus possibly extending the family of exotic nonlinear reflection processes.

Improved adaptive notch filter-based active damping method for shunt active power filter with LCL-filter

The LCL-filter has been recently used with grid-connected converters to mitigate switching ripple harmonics. The LCL-filter presents a better attenuation performance for switching ripple harmonics in comparison with L- and LC-type filters. However, the application of LCL-filter has two basic constraints on the circuit design and the resonance problem. These constraints can be effortlessly overcome for grid-connected converters which operate on the utility fundamental frequency. On the other hand, these constraints become a challenging issue when the LCL-filter is used with shunt active power filter (SAPF) because of the wide operation frequency bandwidth of SAPF. This wide operation bandwidth of SAPF causes a narrow bandwidth for the selection of LCL-filter cutoff frequency and the resonance damping control. In this paper, the application constraints of LCL-filter are discussed and the LCL-filter design is provided for SAPF. In addition, an adaptive notch filter-based single-loop active damping method is developed considering the wide operation bandwidth of SAPF. The proposed method consists of a grid impedance estimation algorithm in order to update notch filter parameters adaptively against grid impedance variations. By the help of the single-loop active damping strategy, the proposed controller does not require any additional sensor for the current measurement of LCL-filter capacitor to damp resonance currents. The stability analysis of proposed controller is performed through pole–zero maps. The proposed method is tested, and its performance is verified with comprehensive case studies of a 400-V 80-kVA SAPF simulation model through MATLAB/Simulink.

A new lumped parameter model for the design of the free-flooded ring transducer

The free-flooded ring (FFR) transducer is the well-known low-frequency sound sources in underwater because of its broad operating frequency bandwidth and relatively small size. Many previous studies have been performed that predict the characteristics of an FFR transducer using an equivalent circuit model (ECM), a type of lumped parameter model (LPM) because an ECM is widely used to understand the properties of such transducers in the design process. However, it is quite difficult to predict the characteristics of an FFR transducer because the acoustic field is generated from its top and bottom openings, connected by the inner fluid, as well as the cylindrical ring surface. In this study, the authors investigated an ECM of an FFR transducer. The ECM consists of three parts: the piezoelectric ring, the cylindrical cavity, and the radiation load. In addition, an LPM which can consider mutual radiation loads was proposed to improve the accuracy of the model. The proposed models were compared and verified using commercial finite element method (COMSOL Multiphysics). We confirmed that LPM can predict characteristics of FFR transducer more accurately than ECM. [This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (Grant No. 2016R1E1A2A02945515).]

Broadband Circularly Polarized Filtering Antennas

This paper consists of two parts. The first part presents a review of the recent development in broadband circularly polarized filtering antennas. The second part presents a novel design of broadband integrated filtering antenna based on eighth-mode SIW (EMSIW) resonators for rectenna applications. This work has three main novel contributions. First, by adjusting the external quality factors and coupling coefficients of the resonators in this filtering antenna, optimum input impedance with a complex value can be realized within the filtering antenna. Thus there is no need for an external impedance matching network, which is usually required between the antenna and the rectifying circuits; Second, compared with traditional microstrip resonators, high-Q EMSIW cavities are used to increase antenna gain; third, the coupling gap between the EMSIW resonators also acts as the feeding structure of the radiator. So the feeding structures are all on the middle layer. The ground plane on the back side is a complete structure without any defects. This novel structure design improves front-to-back ratio to enhance the antenna receiving efficiency. To validate this method, two C-band circularly polarized integrated filtering antennas with an input impedance of 50 $\Omega $ and complex impedance are designed, simulated, and fabricated. The measured results show that the operating frequency bandwidth of the proposed antennas is more than 14.5% at C-band with the gain above 8 dBi. The 3-dB axial ratio bandwidth is larger than 8.5% and the front-to-back ratio is higher than 18 dB. Moreover, the proposed antenna with complex impedance is conjugate matched with the input impedance of a specific rectifying circuit at 5.8 GHz and harmonics suppression at the second-harmonic frequency is achieved.

Construction of a Multiway Carbon Nanotube Loudspeaker with Finely Tunable Resonance Frequencies

AbstractThe sound pressure generated by thermo‐acoustic (TA) loudspeakers is proportional to the frequency of the sound. This characteristic yields a low sound pressure level (SPL) in the low‐frequency region, hindering the practical application of TA loudspeakers. The limitation of low SPL is approached by using a resonating structure, in which a TA sound generator, such as multiwalled carbon nanotube sheet, is enclosed within a cavity covered by a vibrating plate. However, the cavity‐plate resonator produces an amplified SPL only around the resonating frequency, so its operating frequency bandwidth is narrow. Hence, a multiway TA loudspeaker consisting of multiple resonators that can amplify sound over a wide frequency range is designed. An accurate mechanical model is presented for predicting the resonance frequency and it shows that the behavior of resonators designed from the proposed model matches the theory well. The model enables the fine‐tuning of resonances through the application of different materials for a resonator plate and by changing the structural dimensions. A crossover network for combining multiple TA resonators is designed, and the total frequency response shows a flat frequency response with amplified SPL. These improvements open up possibilities for the use of TA loudspeakers as a practical audio device.

Broadband GaN HEMT distributed power amplifier design with phase adjustment

AbstractThis letters presents a new wideband power amplifier approach to achieve high performance of wideband frequency operation from low frequency such as 80–2100 MHz for two‐way radio applications. The approach is referring to distributed power amplifier with phase adjustment of the gate line network to balance with drain line network (specifically with drain line tapering). Experimental of the prototype level with gallium nitride high‐electron‐mobility‐transistor demonstrated output power of 41 dBm, flat gain at 12 dB, and bandwidth covering 80 MHz to 2.1 GHz with power added efficiency of 45% under 28 V drain bias. According to the author's knowledge, this work has illustrated a significant enhancement in efficiency over the conventional topology, low cost implementation, and offers wideband operation for public safety applications.

A wide-band piezoelectric energy harvester with adjustable frequency through rotating the angle of the jointed beam

ABSTRACTIn this paper, we investigate the effects of a jointed beam system on the performance of a piezoelectric energy harvester. An experimental model composed of three piezoelectric plates attached to three aluminum beams was used for testing. Each aluminum beam has an additional jointed beam rotating freely. The rotating jointed beam is used to adjust the operational frequency of the piezoelectric energy harvester. This multi-beam system enables a wider operational frequency bandwidth of the energy harvester and therefore increases the energy harvesting efficiency.

Uniplanar Y and L shaped ACS fed multiband and wideband compact printed antenna for advanced wireless communication systems

In this paper, a very small size (14 × 20 mm2), tunable printed antenna consisting of Asymmetric Coplanar Strip (ACS) feedline with three radiating elements with half wavelength (inverted U-shape and rectangular-shaped) is developed for WLAN IEEE 802.11 a/b/g, WiBro, LTE and WIMAX communication applications. By adjusting the location and lengths of each elementary radiating elements, three individual current itinerary can be induced which accompanied to excitation of three individual wide operating frequency bands. Thereupon, the measured and simulated return loss (S11) results are examined and its analysis is demonstrated along with its evolution, Z parameters, and realized peak gain with radiation patterns properties. The operating bandwidths (VSWR < 2) are about 100 MHz from 2.3–2.4 GHz, 155 MHz from 3.4–3.55 GHz and 2.45 GHz from 4.15–6.6 GHz, respectively. Henceforth, the developed structure can be easily incorporated into more developed and sophisticated portable systems that endures WLAN (5.20/5.80), LTE2300, WiBro (2300 MHz), US public safety band (in the vicinity of 4.9 GHz resonant mode) and WiMAX (3.50/5.50) communication standards.

Exploiting bistable oscillator subharmonics for magnified broadband vibration energy harvesting

Recent research on primary battery alternatives for supplying autonomous wireless devices has recently highlighted the advantages of nonlinear oscillators' dynamics and more particularly bistable oscillators' behavior for ambient vibration harvesting. The key property of bistable oscillators compared to linear ones is their enhanced operational frequency bandwidth under harmonic excitation, potentially leading to a better adaptation to the environment. However, the classical frequency response characterization of such devices does not reveal all the possible dynamic behaviors offered by bistable oscillators. Thus, subharmonic motions are experimentally investigated in this letter, and their energy harvesting potential as well as their ability to enhance the bistable generator bandwidth is evaluated. The results obtained with a generator integrating buckled beams for the bistability feature show that, in addition to the commonly considered harmonic behavior, subharmonics allow widening of the useful operating frequency band of the bistable microgenerator by 180% compared to the sole exploitation of the first harmonic motion.

Multi feed multi band uniplanar ACS fed antenna with N shape and inverted L shape radiating branches for wireless applications

In this research, a compact uniplanar multiband asymmetric coplanar strip-fed triple band monopole antenna is presented for WLAN/WiMAX applications. The designed antenna consists of an N and modified L-shaped strips and lateral coplanar ground plane for multiple wide operating frequency bands. The geometry is designed on the substrate FR4 to work over three bands from 2.45 to 2.6, 3.4–3.7 and 4.5–6.3 GHz with resonant frequencies of 2.5, 3.5 and 5.8 GHz for return loss S11 < − 10 dB. The uniplanar antenna is simulated using CST MWS software and tested using PNA N5222A vector network analyzer (Agilent technologies) and anechoic chamber. Measured results are confirmed with simulated results. Nearly, omnidirectional and bidirectional patterns with constant gain is achieved in all the operating bands. The easy feeding technique, wide impedance bandwidth, cost effective and very small in size makes it a best candidate for advanced compact wireless systems.

A new lumped parameter model for the design of the free-flooded ring transducer

The free-flooded ring (FFR) transducer is the well-known low-frequency sound sources in underwater because its operating frequency bandwidth is broad and relatively small size. Previous researches were preformed to predict the characteristics of FFR transducers using ECM which is a type of LPM because ECM is widely used to understand its characteristics in transducer design process. However, it is hardly to predict the characteristics of an FFR transducer because the acoustic field is generated from its top and bottom openings, connected by the inner fluid, as well as the cylindrical ring surface. Here, the authors investigated an ECM of an FFR transducer consisting of three parts: the piezoelectric ring, the cylindrical cavity, and the radiation load. In addition, an LPM which can consider mutual radiation loads was proposed to improve the accuracy of the model. The proposed models were verified using commercial finite element method (COMSOL Multiphysics). It was confirmed that LPM could predict characteristics of FFR transducer more accurately than ECM. [Work supported by NRF 2016R1E1A2A02945515).]

3D-Printed Super-Wideband Spidron Fractal Cube Antenna with Laminated Copper

In this paper, a 3D-printed super-wideband (SWB) Spidron fractal cube antenna is proposed. The Spidron fractal configuration is utilized as a self-complementary structure on each face of a 3D frame to attain SWB characteristics. The antenna is excited through a tapered microstrip balun for both mode transforming and impedance matching. A prototype of the proposed antenna, including the 3D frame fabricated with the help of a 3D printer and Spidron fractal patches made of copper tape, is experimentally verified. The measured −10 dB reflection ratio bandwidth is 34:1 (0.44–15.38 GHz). The peak gain varies from 3.42 to 9.29 dBi within the operating frequency bandwidth. The measured radiation patterns are nearly omnidirectional at all operating frequency bands.

A Proposed Design of Unit Cell of Metamaterial for 5G Mobile Communication

In this manuscript a design of metamaterial unit cells which are new artificial materials made of periodic arrangement much smaller than the guided wavelength, are proposed which are suitable to work for 5G mobile communication working with millimeter frequency band at 28 GHz due the high demand for the frequency spectrum for mobile networks .The structures of unit cells were simulated using High Frequency Structure Simulator HFSS software. The design starts with the metamaterial structure which is composed of double rectangular (DRR) and circular split ring resonator (DSRR). The results of simulation showed very good results such as wide operating frequency band which is 1.34 GHz with very law radiation losses the unit cell designed to overrun the radiation losses which are appear with the work of metamaterials.

A 75 GHz regenerative dynamic frequency divider with active transformer using InGaAs/InP HBT technology

This letter presents a high speed 2:1 regenerative dynamic frequency divider with an active transformer fabricated in 0.7 μm InP DHBT technology with of 165 GHz and of 230 GHz. The circuit includes a two-stage active transformer, input buffer, divider core and output buffer. The core part of the frequency divider is composed of a double-balanced active mixer (widely known as the Gilbert cell) and a regenerative feedback loop. The active transformer with two stages can contribute to positive gain and greatly improve phase difference. Instead of the passive transformer, the active one occupies a much smaller chip area. The area of the chip is only and it entirely consumes a total DC power of only 94.6 mW from a single −4.8 V DC supply. The measured results present that the divider achieves an operating frequency bandwidth from 75 to 80 GHz, and performs a −23 dBm maximum output power at 37.5 GHz with a 0 dBm input signal of 75 GHz.

Half‐mode substrate integrated waveguide‐based leaky‐wave antenna loaded with meandered lines

A novel meandered-line-loaded leaky-wave antenna (LWA) is proposed. Two half-mode substrate integrated waveguide-based LWAs are placed face to face for obtaining high peak gains, and the meandered lines are introduced to acquire larger ratio of the beam scanning range to the operating frequency bandwidth. It is demonstrated that the operating frequency band can be narrowed by almost 1 GHz due to the meandered-line structure under the condition that the scanning range keeps unchanged. The proposed LWA is fabricated and measured. Both simulated and measured results indicate that the designed antenna is a balanced LWA operating in frequency band 10.8–16 GHz (5.2 GHz centred at 13.4 GHz). Continuous beam scanning characteristic is observed from −60° to +34°, and comparisons are given out to validate the proposed design.

A lumped parameter model of the single free-flooded ring transducer.

A free-flooded ring (FFR) transducer can generate low-frequency sound in a small device and has a wide operating frequency bandwidth. Many studies have been performed that can predict the characteristics of an FFR transducer using analytical techniques and an equivalent circuit model (ECM), and methods to predict properties using numerical simulations have recently been developed. However, an ECM, a type of lumped parameter model (LPM), is still widely used to interpret the properties of such transducers in the design process. In this study, the authors investigated an ECM of an FFR transducer. The ECM consists of three parts: the piezoelectric ring, the cylindrical cavity, and the radiation load. Moreover, it can be included readily in a circuit to drive an FFR transducer. Additionally, an LPM was proposed, considering the mutual radiation loads, to improve the accuracy of the model. Each model was tested in comparisons with the finite element method; it was confirmed that an LPM could predict the properties of an FFR transducer with much better accuracy than an ECM. The LPM developed can save much time in designing FFR transducers.

Design and analysis of a multi-step piezoelectric energy harvester using buckled beam driven by magnetic excitation

In this paper, a multi-step buckled beam piezoelectric energy harvester driven by magnetic force is proposed. To convert ambient mechanical vibration into electrical energy with increased operational frequency bandwidth and power density, the harvester utilizes a combination of multi-step mechanism and bistable structure. A multi-step mechanism in the form of a magnet array with staggered magnetic poles has been designed for the energy harvesting system to obtain a wide working bandwidth. A buckled beam as a bistable structure enables the harvester to demonstrate a high-voltage output. A theoretical model is developed to characterize the multi-step piezoelectric energy harvester. Both simulations and experiments on the fabricated experimental device are carried out to validate the design and analysis of the multi-step piezoelectric energy harvester. The experimental results indicate that output open circuit voltage of the harvester is 4.4V. The harvester generates a peak power of 5.0μW across resistive load of 3.3 MΩ at the frequency of 3.0Hz. The results show that the device can cause stable output voltage under wideband excitations. Furthermore, under the multi-step mechanism, the magnet array with staggered magnetic poles increases the output voltage of the harvester by 25.0% compared to the unidirectional magnetic pole arrangement.

Parameter tuning of piezoelectric–electromagnetic hybrid vibration energy harvester by magnetic force: Modeling and experiment

Traditional piezoelectric–electromagnetic hybrid vibration energy harvesters (HVEH) cannot tune their own characteristics easily once they are manufactured. To overcome this limitation, a novel tunable PE&EM-VEH is reported in this article. It employs a magnetic tuning technique to realize the double tuning ability at the same time including the operating frequency tuning and the coupling effect tuning. The magnetic tuning technique is based on a well-designed closed magnetic circuit instead of the isolated magnet model. Furthermore, a distributed parameter model of an axial tensile forced cantilever beam with a tip mass is set up for calculating the operating frequency as a function of the air gap; meanwhile, a lumped parameter model of a closed magnetic circuit is introduced for computing the nonlinear magnetic attractive force and the equivalent electromagnetic force-current factor as a function of the air gap. To verify the theoretical developments, a tunable HVEH prototype was fabricated and tested. The prototype can achieve a wide operating frequency bandwidth ranging from 25.5Hz to 62Hz, a variable dimensionless piezoelectric squared force-voltage factor ranging from 0.031 to 0.135 and a variable dimensionless electromagnetic squared force-current factor ranging from 0.172 to 1.073 by tuning the air gap, which agrees with the theoretical model. In addition, the maximum resonance power output of the prototype is 3.32mW at the air gap of 12mm under 0.3g base acceleration. It also achieves 2.78mW average power output over the operating frequency range.